The invention relates to a knock sensor for an internal combustion engine. In such a knock sensor, for example one as known from the U.S. Pat. No. 4,966,031, the piezoelectric disk is arranged between two contact disks, each of which is covered by an insulating disk. In all cases, however, these insulating disks consist of electrically non-conductive material. However, in piezoelectrical materials, it is possible at high temperatures, in particular during temperature changes, for electrical charging to take place which can result in high electrical voltages. This can possibly result in faulty measuring and interference in the connected circuit.